Collaborative Research: Comprehensive Analysis of Seismic Processes in a Deep South African Mine

地震物理学中的许多基本问题仍未解决，主要是因为难以获得小地震的高质量近源记录和获得可靠的震源参数。该项目的总体目标是提供对大震级范围（大约-4到4级）的震源过程的更好理解。我们正在对南非一个3.6公里深的矿井中几种不同类型的地震事件（地震、岩爆和爆炸）的震源特性进行详细的地震学调查。我们还将开展一项短场运动，记录震级范围极端和靠近断层结构的地震事件。全源张量反演、秒矩分析和频谱方法将用于确定源属性的综合集合，包括标量势/矩、震源机制、角频率、应变/应力降、辐射能量、破裂速度和源时间函数。将特别致力于探测断层的各向同性成分。对不同事件类型的预期辐射的理论计算将有助于对结果的解释。将上述分析应用于小震级、近震源地震数据，将允许获得地震物理的许多方面的约束，包括成核过程、地震辐射各向同性分量的普遍性、随着事件震级或与地质和采矿结构的接近而发生的破裂物理变化，以及地震、爆炸和其他震源之间的震源参数差异。关于震源性质和标度关系的高分辨率结果将通过帮助解决关于地震成核和破裂过程、将实验室结果标度到自然断层和地震能量预算等方面的长期争议，对地震物理学和岩石力学界产生重大影响。此外，空间相关地震特性的研究结果将有助于决策何时何地暂停采矿活动以提高地下安全

Many fundamental questions in earthquake physics remain unresolved, largely because ofdifficulties in obtaining high-quality, near-source recordings of small earthquakes andderiving reliable source parameters. The overarching goal of this project is to provide animproved understanding of earthquake source processes for a wide magnitude range(approximately -4 to 4). We are performing detailed seismological investigations ofsource properties that characterize several distinct classes of seismic events (earthquakes,rockbursts, and blasts) in a 3.6 km deep South African mine. We will also conduct a shortfield campaign to record seismic events at the extremes of the magnitude range and inclose proximity to fault structures. Full source tensor inversions, second momentanalysis, and spectral methods will be used to determine comprehensive sets of sourceproperties including scalar potencies/moments, focal mechanisms, corner frequencies,strain/stress drops, radiated energies, rupture velocities, and source time functions.Special effort will be devoted to detecting isotropic components of faulting. Theoreticalcalculations of expected radiation from different event types will help in theinterpretation of results.Applying the above analysis to the small-magnitude, near source seismic data will allowus to obtain constraints on many aspects of earthquake physics including nucleationprocesses, the prevalence of isotropic components of seismic radiation, changes in thephysics of rupture with event magnitude or with proximity to geologic and miningstructures, and source parameter differences between earthquakes, explosions, and otherseismic sources. The high-resolution results on seismic source properties and scalingrelations will significantly impact the earthquake physics and rock mechanicscommunities by helping to resolve long-term controversies on earthquake nucleation andrupture processes, scaling of laboratory results to natural faults, and earthquake energybudgets, among others. In addition, the findings on spatially dependent seismic propertieswill be useful for decision-making concerning when and where to suspend miningactivities to enhance underground safety